Devices are commercially available for placement into a fluid stream to reduce noise otherwise resulting from a jet or other highly concentrated fluid stream flowing in a conduit and through standard pipeline components, such as control valves, line connectors, pipeline instrumentation, etc. One example of such a noise attenuator is described in U.S. Pat. No. 4,402,485 (A. Fagerlund), owned by the present assignee. This patent describes a plurality of nested perforated tubes eccentrically arranged and disposed in substantially parallel relationship to each other along the axis longitudinal of the conduit.
Generally, such noise attenuators as shown in the aforementioned patent as well as other proposed structures are located in a conduit adjacent and immediately downstream of a fluid control valve, such as a rotary valve. Thus, the normal fluid noise resulting from the turbulent flow of a jet stream upon initiating opening and closing of the control valve will be attenuated by such noise attenuating devices. More recently, commercial noise attenuator devices have become available in which the noise attenuator is mounted within a rotary control member of the fluid control valve in a combined structure. The combined structure is generally desirable in order to ease the maintenance of such fluid control valves in that removal of the rotary control member simultaneously removes the noise attenuator for servicing or routine maintenance. This combination also is desirable so as to aid in obtaining standard valve flange face to face dimensions for valves with or without a noise attenuator device.
One such commercially available combined rotary control and noise attenuator device utilizes a series of perforated attenuator plates mounted in the bore of a full ball control member or mounted to a segmented ball control member. Generally, such perforated attenuator plates are arranged parallel to each other and are maintained spacially mounted from the ball member by several fasteners perpendicular to the plates. In operation, a concentrated fluid stream immediately encounters a perforated plate across the valve opening and the full incoming stream must pass through the plate perforations as the valve is initially opened to form many minute flow streams due to the perforations.
Certain presently available rotary valve noise attenuator devices utilize many components which are fastened together in a non-secure manner so that occasionally one or more components disengage and are carried downstream of the valve to undesirably interfere with the pipeline system while also obviously degrading the noise attenuator performance.
It is now desired to provide a rotary valve noise attenuator device which is easier and less costly to manufacture yet provides increased noise attenuation compared to presently known proposed or commercial devices. Also, it is desired to provide a reliable operating rotary valve noise attenuator device having improved structural integrity.